Ext JS or Ext GWT

All that stuff in the Secha.io video, about user registration, groups, syncing, messaging and sharing data. That's exactly what I need. The Sencha.io Docs overview page says:

"As she conducts her business that week, she enters expense data into the app -- perhaps even photographs of receipts -- and whenever her device is in range of the network the app synchs all the data with the cloud through Sencha.io Data."

So data definitions are declared as XML and JASON objects in ExtJS, in the Data Store, and are not relational. (??) If I want to access a relational db then I need Ext GWT and a remote server. Right?